The present invention relates to paging reception assurance in a multiply registered (multihomed) wireless transceiver, and more particularly to assuring reception of pages in a multiply registered wireless transceiver wherein page receipt must be guaranteed on at least one system with which the transceiver is registered. Even more particularly, the present invention relates to assuring paging reception in a multiply registered wireless transceiver wherein page receipt must be guaranteed in at least one system having a plurality of paging schemes with which the transceiver is registered.
Great advances in the field of wireless communications have been made over the past ten to twenty years, and continues to be made. These advances both improve the quality of communication, e.g., the clarity and reliability of communication, and improve the geographic coverage of such wireless communications. As industry strives to provide a wireless communications capability that covers the entire globe, factors such as economic viability dictate that space-based transceivers be employed as opposed to ground infrastructure based on cellular (including personal communications services, PCS). Ground-base infrastructure, however, remains technologically advantageous and economically preferable in identified population centers where a great deal of bandwidth is required in a relatively small area. Thus, two types of wireless communication, i.e., ground infrastructure cellular, and space-based satellite systems have emerged.
In addition, different regions of the world have adopted different wireless communication standards, and subscriber units, i.e., wireless transceivers, designed to function in one standard will generally not function in another, at least simultaneously. In regions serviced by more than one standard, it may be advantageous to maintain service on multiple systems, under multiple standards, simultaneously, for maximum reachability, especially in fringe areas and/or when the multiple systems do not cooperate with one another to deliver page messages to the wireless transceiver. These multiple systems may be entirely earth based, may be a combination of earth and satellite based, or may be entirely satellite based.
In order to comply with some existing standards, such as the Global System for mobile telecommunications (GSM), a subscriber unit must be compliant with the standards. Problematically, existing standards may not be designed to cooperate with one another. For example, the GSM requires that a wireless transceiver not miss a GSM page message when in idle mode, and when registered with a GSM network. At the same time, however, the wireless transceiver should not miss pages from other systems with which it is operating simultaneously.
It is expected that each system with which a wireless transceiver operates will maintain a paging schedule within respective broadcast control channels (BCCH), however, each broadcast control channel is independent and asynchronous in time, thus preventing the wireless transceiver from knowing in advance when to schedule monitoring for paging messages at each control channel. Furthermore, the wireless transceiver should only be expected to monitor one broadcast control channel at a time, because processors and other hardware within the wireless transceiver may be shared by each of the systems on which the wireless transceiver operates, thus making simultaneous monitoring on two or more wireless systems impossible.
In the case of GSM, the situation is further complicated by the fact that GSM has a large number of schemes (or paging schedules) for organizing its paging message broadcasts within its broadcast control channel, and by the fact that, in the case where a GSM system is to be employed in conjunction with a satellite-based system, a single satellite spot beam or paging area may encompass many GSM cell sites, all of which may be operating under different and asynchronous paging schedules.
Coordination of paging on two or more simultaneously registered wireless systems, is further complicated by the fact that a large number of subscriber units are battery powered, and therefore maximizing, "sleep mode" time, where little or no battery current is drawn, is highly desirable. Thus, a paging schedule is generally employed by the subscriber unit in order to define those periods during which the subscriber will monitor a paging channel for a page. Outside of these times, the wireless transceiver may shut down, and therefore be unresponsive to pages. Thus, the wireless transceiver must know in advance of any page messages being sent, the time periods, for each system it is monitoring, during which a page message can potentially be transmitted by the respective system.
In accordance with the GSM system, and similar systems, the paging channel may be expanded for one or more frames by the addition of a paging channel extension bit. In the case of GSM, the paging channel extension bit tells the affected wireless transceiver to monitor the "next but one" paging channel within the GSM broadcast control channel. While this extension capability allows minimization of the number of paging channels that need to be monitored by a subscriber unit on an on-going basis, and thus improvement in battery life, the possibility of paging channel extension further complicates the goal of paging channel coordination, i.e., ensuring that paging channels from each of two or more systems with which a subscriber unit is registered do not occur simultaneously.